Telephone system



UNITED STATES PATENTy Ortner:e

THOMAS V. OBRIEN, OF WILKES-BARR, PENNSYLVANIA..

TELEPHONE SYSTEM.

SPECIFICATION forming part of Letters Patent No. 469,865, dated March 1, 1892.

Application iiled November 12, 1890. `Serial No. 371,228. (No model.)

To @ZZ whom it may concern.-

Be it known that 1, THOMAS W. OBRIEN, a citizen of theUnited States, residinginWilkes- Barr, in the county of Luzerne and State of Pennsylvania, have invented certain new and useful Improvements in Signaling Apparatus for Electrical Intercommunication Systems, of Which the following isa specification.

My invention relates to that class of elec-v a greater or less number of lines of electrical intercommunication radiate in different directions to a corresponding number of substations, such an organization being especially adapted to the requirements of police and fire alarms, district-messen ger calls, and espe# cially telephonie-exchange service, to any or all of which my invention may with advantage be applied. In such an organization it is necessary that signalizing devices shall be provided at each terminal of each of the several independent radiating lines-that is to say, there must be a signalizing apparatus connected With each line atits corresponding substation adapted to be actuated from the central station to call the attention of such substation when required, and in like manner there must be at the central station an independent sgnalizing device or apparatus otl some character connected with each individual line capable of responding to and properly indicating a signal transmitted from any of the sub-stations. The signals or indications produced at the central and at the substations may be either audible or visual, or both; but in practice it is usually found preferable to make use of an audible signal at each of the sub-stations and a visual signal in connection with each individual line at the central station, and this latter may be supplemented by an audible signal, it' ci rcu m stances require.

The object of my invention is to enable all the signals required in such a system, whether sent from the central station to any one of the sub-stations or from any one of the sub-stations to the central station, to be transmitted by means of one electrical generator or signal-transmitter common to the Whole system, Which common generator is by preference situated at the central station,thereby rendering unnecessary the provision, as heretofore, of a separate signal-transmitter at each sub-station.

The accompanying drawing is a diagram representing the application of my invention to a system consisting of a central station and two sub-stations B and C, though it is to be understood that the number of said sub-stations may be indefinitely increased Without departing from the principle of my invention.

In the diagram,I G represents the electric generator or signal-transmitter at the central station. purpose a small dynamo or magneto-generator driven by any convenient power and constantly transmitting or tending to transmit an alternating current; but any Well-known substitute for this apparatus may be usedsuch,f0r example, as a battery and circuitbreaker. One pole of this generator is permanently connected to the earth at the central station by a wire g, While its opposite pole is connected to a looped line Wire LL, which goes out through the Whole geographical district embraced within the system, and preferably, though not necessarily, returns to the same'pole of the generator. Branches or legs are permanently connected with the loop L L at various points, as required, each of Which extends to and terminates in an insulated contact-point in a sub-station. These branches are shown at A, B, O, D, and E, the number of them being Wholly immaterial.

The arrangement of the apparatus and circuits at each one of the sub-stations is precisely the same. For example, the apparatus at sub-station B consists of signalizing apparatus S (here shown as an electro-magnetic bell) and a common three-point key K. One terminal of the bell S is attachedto the individual line B', which extends directly to the central station, terminating there in a metallic peg B2 or other equivalent device, While the other terminal of the bell is connected at the point 1 to the lever ot the key K. The key K normally makes contact with the stop 2 and ground-wire g', but when depressed leaves the point 2 and touches the point 3,

It is preferred to employ for this y IOO thereby establishing contact between the individual wire B and the branch B of the signaliZing-circuit L L, as hereinafter more fully explained.

At the central station the metallic peg B2, which forms the terminal of the individual wire B', is normally thrust into a metallic socket, thereby making contact with t'he individual signaling device b, (which is here shown as an annunciator-drop or `equivalent visual signal, but which might be an audible signal, if preferred.) The other terminal of this signalizing device is permanently connected to the ground-wire g3.

P is a metallic plate, which is electrically connected bot-h with the signalizing-circuit L L and the free terminal of the generator G.

It will be understood that the signalizingcircuit L L, its branches A B C D E, &:c., and the plate P are all electrically connected together and are all normally insulated from the earth.

This apparatus is the substantial equivalent of the common th ree-point key or switch, in which the metallic peg attached to the fiexible cord performs the function of the lever of the key, while the socket corresponds to the resting contact and the plate P to the lworking contact of the key.

`The operation of the apparatus is as follows: In case the attendant at the central station Wishes to call the attention of the attendant of sub-station B,for example,he removes the peg B2 from its socket and touches it to the plate P, (this device being the electrical equivalent of such a three-point key as that shown at K.) .The circuit is completed and a current instantly flows from thegenerator G, through the plate P. peg B2, and wire B', to the signal-bell S at the sub-station B, and thence through the contact 2 of key K and wire g to the earth. 1f it had been desired to signalize the sub-station C instead of B, it would have been done in the ,same manner by touching the peg C2 instead of B2 to the same plate P and actuating the signalbell S. This apparatus and mode of operation is well-known in the art and in itself forms no part of my invention. In case any one of the sub-stations-for example, sub-sta` tion B-desires to transmit a signal to the central station the attendant depresses the key K, which detaches thel line B from the ground wire g and makes a new contact at the point 3. A current now fiows from the generator G through the signalingcircuit L L and branch B and thence through the signalbell S, individual line B', peg B2, signal apparatus b at the central station, and so to the ground g3. The particular signal'apparatus which is actuated indicates the corresponding sub station from-which the signal proceeded. As soon as the signalizer releases the key K the contact with the ground g is restored, thus enabling the attendant at the central station to respond to the signal, if desired, by merely touching the peg B2 to the plate P, `as before. The operation in case of sub-station C or of any other ot' the stations D E, dsc., (not shown in detail,) is the same in every particular.

It is obvious that two or more insulated looped signalizing-circuits might be extended from the same pole of a common generator, or that an independent generator might be employed at the central station in connection with the plate P-as, for example, in case it were desirable that the signals in one direction should be distinguishable from the signals in the other direction by their different rate of vibrationwithout departing from the spirit of my invention.

I claim as my inventionl. The combination, substantially as hercinbefore set forth, of an electric generator at a central station, having one of its poles connected to the earth and the other to a normally-open signalizing-circuit provided with permanent branches extending to two or more sub-stations, indicating apparatuses corresponding in number to said sub-stations, each such apparatus having one of its `terminals connected to earth at the central station and the other to a line extending to a corresponding sul) station, and a normallyopen key at said sub-station, which when closed connects said line with the common signalizing-circnit, and thereby actuates the corresponding sign al apparatus at the-central station.

2. The combination, substantially as hereinbefore set forth, of an individual line extending froin a central to one of two or more sub-stations, a key at each of said sub stations, having its resting-contact connected directly to the earth, a key in each individual line at the central station, having Aits restingcontact connected to the earth through asig naling or indicating device, and a generator of electricity having one of its -terminals connccted to the earth and its other terminal common to the working contacts ofthe keys, both at the central station and at the several sub-stations.

In witness whereof I have hereunto anixed my name in the presence of two subscribing witnesses.

THOMAS W. OBRIEN.

Witnesses:

J. EMMET OBRIEN, HOWARD M. STREETER.

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